Perhaps the most obvious is to improve precision, which is a function of manufacturing and assembly tolerances, gear tooth surface finish, and the guts distance of the tooth mesh. Sound is also suffering from gear and housing materials as well as lubricants. In general, expect to pay out more for quieter, smoother gears.
Don’t make the mistake of over-specifying the motor. Remember, the input pinion on the planetary must be able deal with the motor’s result torque. Also, if you’re utilizing a multi-stage gearhead, the output stage must be strong enough to soak up the developed torque. Certainly, using a more powerful motor than required will require a bigger and more expensive gearhead.
Consider current limiting to safely impose limitations on gearbox size. With servomotors, result torque is certainly a linear function of current. So besides safeguarding the gearbox, current limiting also shields the motor and drive by clipping peak torque, which may be from 2.5 to 3.5 times continuous torque.
In each planetary stage, five gears are concurrently in mesh. Although it’s impossible to totally eliminate noise from this assembly, there are many ways to reduce it.
As an ancillary benefit, the geometry of planetaries fits the shape of electric motors. Therefore the gearhead can be close in diameter to the servomotor, with the result shaft in-line.
Highly rigid (servo grade) gearheads are generally more costly than lighter duty types. However, for rapid acceleration and deceleration, a servo-grade gearhead may be the only wise choice. In such applications, the gearhead may be viewed as a mechanical springtime. The torsional deflection low backlash planetary gearbox resulting from the spring action adds to backlash, compounding the effects of free shaft motion.
Servo-grade gearheads incorporate a number of construction features to reduce torsional stress and deflection. Among the more common are large diameter result shafts and beefed up support for satellite-equipment shafts. Stiff or “rigid” gearheads have a tendency to be the most costly of planetaries.
The type of bearings supporting the output shaft depends on the strain. High radial or axial loads generally necessitate rolling element bearings. Small planetaries can often get by with low-price sleeve bearings or other economical types with relatively low axial and radial load capacity. For larger and servo-grade gearheads, heavy duty result shaft bearings are usually required.
Like the majority of gears, planetaries 
make sound. And the quicker they operate, the louder they get.
Low-backlash planetary gears are also available in lower ratios. While some types of gears are generally limited by about 50:1 or more, planetary gearheads prolong from 3:1 (one stage) to 175:1 or more, depending on the number of stages.